[rtems-tools] Fix shlex.join on python 3.8 and earlier

[Chris Johns]

On 31/8/2023 4:14 am, Frank Kühndel wrote:
> Hello Chris,
> 
> if I did not make any mistake, this patch works fine on OpenSUSE 15.5.

Thanks, I have pushed the change.

> I had some headaches because the source-builder tries to download the
> rtems-tools as tar.bz2 and the version with the patch is not yet on that server.
> I fumbled your patch into the cached tar.bz2. That seemed to work in the end.

Ah, a clone of rtems-tools and then a `distclean configure` showed the issue :)

Chris